Many consumer products in use today have embedded RF wireless communication elements. Wireless consumer products ideally require low power consumption and low cost. One strategy for low power consumption (i.e. power conservation) in low data rate applications is to use a device that normally includes at least one oscillator in a mode of bursts of very high rate data streams, separated by “sleep” modes during which the device consumes very little current. However, this strategy has a problem in that the wake-up time of the device's oscillator could be quite long, i.e. several microseconds. This makes such a strategy unattractive.
Typically, an oscillator includes a quartz crystal as a resonance element. Quartz crystals are well known in the art. A quartz crystal is characterized by a very precise resonance frequency or “accuracy”, and a very high quality factor marked as “Q”. The quality factor is the ratio between the energy installed in the crystal and the energy wasted in every cycle of oscillation. In order for the oscillator to “wake-up” at the start of an oscillation cycle, one needs to take a signal introduced on the resonator feeds, amplify it and feed it back into the resonator. The initial signal on the resonator feeds is white noise, which has the bandwidth of the resonator and the amplitude of the equivalent resistance of the resonator. Because this signal is very small, one needs to wait a long time for the energy in the resonator to build lip.
Circuits and methods for fast wake-up or “kick-starting” an oscillator are also known. In particular, there are known methods and circuits that use energy other than white noise to kick-start an oscillator. For example, U.S. Pat. No. 5,805,027 to Yin (hereafter “Yin”) teaches a transistor circuit for fast start up of a crystal oscillator. A voltage pulse from a pulse generator 30 is mirrored to the gain stage comprised of transistors T6, T7 and T8 to make a current pulse that causes the crystal to start oscillating. In another example, U.S. Pat. No. 6,057,742 to Prado (hereafter “Prado”) teaches a crystal oscillator in which a noise generator 16 applies the voltage waveform illustrated as a curve 50 in his FIG. 4 to an input 12A of an oscillator circuit 12. However, both Yin's and Prado's use of a single “kick” pulse has a major disadvantage: it provides a wake-up time that is still far too long in comparison with the times achievable with the method and system of the present invention, i.e. wastes energy. By providing a single interrogating pulse to the crystal resonator, one does not fully utilize the potential of awakening the crystal oscillator in a fast and efficient manner.
There is therefore a widely recognized need for, and it would be highly advantageous to have a fast wake-up oscillator that does not suffer for the disadvantages listed above.